Researchers at the Scripps Research Institute in Florida have recently shown why exercising intensely makes you stronger and faster and gives you greater endurance (EMBO J, May 2, 2014;33(9):1027-43). When you exercise intensely, you are stressed by the pain in your muscles and by the gasping for breath. When your body is stressed emotionally or physically, a part of your brain called the hypothalamus produces hormones that stimulate your adrenal glands to produce huge amounts of hormones called adrenalin and nor adrenalin. They make your heart beat faster and you breathe faster, widen your pupils, and allow muscles to contract with more force. They make you stronger and faster and more aware of your surroundings.

Adrenalin Causes Cells to Make CRTC2
At the same time, adrenalin and noradrenalin cause cells to make a protein called CRTC2 that stimulates genes in muscle cells to make muscles grow larger and stronger. The more intensely you exercise, the more adrenalin and noradrenalin your body produces, so that your cells make more CRTC2 to make muscles even larger and stronger.

The Study
Mice were specially bred to be able to produce huge amounts of CRTC2. Following a program of frequent intense treadmill running, their endurance doubled in two weeks, compared to an increase of only 8.5 percent with intense exercise in normal mice. The genetically modified mice also developed larger and stronger muscles and had far less fat. This helps to explain why intense exercise can help you to lose fat from your body and prevent and treat diabetes.

What This Means For You
Any exercise is better than no exercise. However, to really improve your fitness level, you have to exercise intensely. If you do not feel burning in your muscles and shortness of breath at least two or three times a week when you exercise, you are not getting a strong enough stimulus to make yourself significantly faster, stronger and have greater endurance.

Background before Peaking
Start your program by going out and exercising at a slow pace until your muscles feel heavy or hurt and then stop. Do this every day and be patient. Eventually most people should be able to go out and exercise at a casual pace for 30 minutes every day. You then will be able to start training.

Stress and Recover During Each Workout
Warm up by exercising at a slow pace until your muscles feel comfortable, usually for five to ten minutes. Then pick up the pace for 10 seconds and then slow down, but do not stop. It is irrelevant how long you slow down. Even the best athletes in the world often take long recoveries between these fast intervals. Then pick up the pace for 10 seconds again and slow down. Alternate these fast-pace pickups and slow downs until your legs start to feel heavy or hurt and then stop for the day.

Alternate-Day Intense Workouts
On the next day, your muscles may feel sore. You can take the day off if you like, but you will become far more fit if you exercise at a slow pace with no fast intervals. Forty-eight hours after your interval workout, you probably will not have sore muscles and can do another interval workout. You will then try to alternate one day of fast interval pickups with the next day of slower exercise. On your interval workout days, try to extend your intense bursts of exercise up to 30 seconds each. If you are not competing, you do not need to extend your intense intervals for longer than that.

Congratulations!
If you can do workouts involving 10-to-30 second increased intensity intervals every other day, and do slow workouts on your recovery days, you will be in great shape, reap more health benefits and probably live longer and be less likely to suffer diabetes, heart attacks, and certain cancers. Best of all, your friends who are still doing casual slow workouts every day won't be able to keep up with you.

Caution: Too Much Intense Exercise Can Harm
Every time that you exercise intensely, you damage muscle fibers. You can tell that this has happened because your muscles feel sore on the next morning. So when muscles feel sore at the start of a workout, you have to exercise at low intensity or take the day off. Too much force on damaged muscles tears muscle fibers to injure them and make you feel sore all the time.

Out-of-shape people who try to exercise intensely are at increased risk for torn muscles and heart attacks. Before you start an intense exercise program, you may want to check with your doctor to make sure that the arteries that lead to your heart are not blocked. People who suffer heart attacks during exercise are usually just starting an exercise program or are increasing the intensity or duration of their exercise.

About the Author: Gabe Mirkin, MD

Sports medicine doctor, fitness guru and long-time radio host Gabe Mirkin, M.D., brings you news and tips for your healthful lifestyle. A practicing physician for more than 50 years and a radio talk show host for 25 years, Dr. Mirkin is a graduate of Harvard University and Baylor University College of Medicine. He is board-certified in four specialties: Sports Medicine, Allergy and Immunology, Pediatrics and Pediatric Immunology. The Dr. Mirkin Show, his call-in show on fitness and health, was syndicated in more than 120 cities.
Read More